Signaling circuits governing palatal shelf growth and patterning. A, Epithelial-mesenchymal interactions via Pax9-regulated Shh-Bmp and Shh-Fgf feed-back loops control growth and patterning of the anterior palate. B, Oro-nasal patterning of the anterior secondary palate is regulated via Fgf7-mediated Shh repression. C, Pax9-regulated expression of Bmp4 and Osr2 in the posterior palatal mesenchyme and Shh in the posterior palatal epithelium is required for appropriate posterior growth of the secondary palate. In addition, Meox2, Barx1 and Mn1-Tbx22 signaling module regulate posterior palatal growth. Grey, palatal mesenchyme; Green, palatal epithelium.